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Nov 2022 p13 q10
1343
The diagram shows the circle \(x^2 + y^2 = 2\) and the straight line \(y = 2x - 1\) intersecting at the points \(A\) and \(B\). The point \(D\) on the \(x\)-axis is such that \(AD\) is perpendicular to the \(x\)-axis.
(a) Find the coordinates of \(A\).
(b) Find the volume of revolution when the shaded region is rotated through 360° about the \(x\)-axis. Give your answer in the form \(\frac{\pi}{a}(b\sqrt{c} - d)\), where \(a, b, c\) and \(d\) are integers.
(c) Find an exact expression for the perimeter of the shaded region.
Solution
(a) To find the coordinates of \(A\), solve the system of equations given by the circle \(x^2 + y^2 = 2\) and the line \(y = 2x - 1\). Substitute \(y = 2x - 1\) into the circle equation:
(c) The perimeter of the shaded region consists of the line segment \(AD\) and the arc length. The arc length is \(\frac{1}{8}(2\pi\sqrt{2})\) or \(\frac{\pi\sqrt{2}}{4}\). Therefore, the perimeter is: